Non-specific microbicide product development: then and now

Despite the identification of HIV-1 as the etiological agent responsible for AIDS nearly 30 years ago, a sterilizing vaccine capable of preventing transmission of the virus remains elusive. In response to struggles on the vaccine development front, significant effort has been devoted to preventing the transmission of HIV with alternative products, technologies, and strategies. One of the early alternative HIV prevention strategies was microbicides, which are topical products that can be used to prevent sexual transmission of HIV either vaginally or rectally. First generation microbicide products were designed to be simple gel formulations comprised of readily available active agents that were inexpensive and broadly active (i.e., non-specific). Unfortunately, despite the clinical investigation of multiple product concepts satisfying these requirements, none were shown to be efficacious in pivotal trials. More recently, microbicide and oral prevention strategies involving highly specific and potent anti-retroviral (ARV) drugs have shown to be efficacious in trials. Although building on these successes continues, these products have a number of issues including potential toxicity with long term use, selection of HIV resistance, and cost. Further, all of the original justifications for non-specific microbicide products remain valid. This review provides a brief history of non-specific microbicide development, outlines the evolution to, and limitations of, ARV based microbicides, and summarizes the current activity on non-specific microbicide product development.